Purification of aqueous liquids from phenols and other accompanying substances



Patented News, 1937 PATENT i OFFICE roamca'non or AQUEOUS mourns mom PHENOLS AND OTHER suasrmvoss ACCOMPANYING Paul Hermann Gericke, Paul, Herold, Helmut Krats, and Eberhard Vogt, Leuna, Germany, assignors to L G. Farbenindustrie Aktiengesellschait, Frankiort-on-the-Main, Germany No Drawing. Application September 5, 1935, Se-

rlal No.- 39,302. In 1934 '1 Claims.

The present invention relates to improvements in the purification oi aqueous liquids from phenols and other accompanying substances.

It has already been proposed to extract dis- 5 solved organic substances, as for example phenols, .irom aqueous liquids from various sources by subjecting the liquids to a treatment with solid adsorption agents, such as active carbon, and then further extracting the adsorbed substances 10 with organic solvents, as .for example, benzene.

after the aqueous liquid has been expelled from r the adsorption chamber by means of the organic solvents by the formation of layers. When the extraction has been completed, the solvent is removed from the active carbon by means or steam.

The solvent is recovered by distillation.

We have now found that a much better eirect is obtained by employing as extracting solvent liquid ammonia instead of the usual solvents, such so as benzene, carbon disulphide or mixtures 01 benacne and alcohol. The procedure mayv for example be as iollows:--

A charging of the adsorption chamber filled for example with active carbon is effected in the usual manner by causing aqueous liquid containing phenols and other accompanying organic substances to flow upwards therethrough. It is advantageous to operate two or more adsorption chambers one behind another. By suitable adiustment of the speed of flow oi the aqueous liquid, the adsorption agent in the first adsorption chamber may be substantially. saturated while the aqueous liquid leaves the second ad- 35 sorption chamber practically free from the accompanying substances. When the adsorption agent in the first chamber is sufliciently charged, the supply oi aqueous liquid thereto is discontinued and the aqueous liquid therein is re- 4 moved. For this purpose gases of all kinds may be used: air is not recommended although its use does not render the process impossible; gases, such as nitrogen or hydrogen are more suitable. The expelling oi the water is advantageously effected by means of ammonia gas from the stock oi liquid ammonia which is necessary for the further carrying out 01' the process. It has been found, contrary to expectation, that the greater part of the water content of the adsorbent-chamher is expelled without adsorption of ammonia. Only the aqueous liquid leaving towards the end 01' the emptying contains absorbed ammonia and is preferably collected separately while the former a portion oi aqueous liquid is. returned to the crude Germany September 28,

aqueous liquid. There is then carried out directly a treatment of the still wet adsorbent within the adsorption chamber by means of liquid ammonia for the extraction of the adsorbed substances, the treatment being carried on until the liquid ammonia leaving the chamber is free from extracted substances. This treatment may be carried out at atmospheric or increased pressure. It is thus possible to regulate the temperature at which the extraction with liquid ammonia is carried out as desired. It is preferable to carry out the said extraction at room temperature or at the same temperature at which the adsorption is carried out in order to render any cooling by evaporation of liquid ammonia unnecessary. The extraction of the said solid adsorption agents proceeds even at temperatures below zero C. so rapidly and thoroughly that the adsorbent has no appreciably reduced adsorptive power even after charging a hundred times or more. For such an extraction it is usually necessary to use about twice or three times the capacity of the adsorption chamber or liquid ammonia during the course of from about one to two hours.

When the extraction has been completed, the adsorption. chamber is emptied of liquid ammoniaythis may be assisted by increasing the vapor pressure 01' the liquid ammonia by heating and then blowing out liquid ammonia adhering to the adsorbent by means of steam. The amount of steam necessary is comparatively small and therefore the amount of pure aqueous ammonia which is preferably collected separately is inconsiderable. It may be employed as such for special purposes but, by reason of its small amount, may also be worked up with the used up extraction agent as explained'hereinafter.

The adsorbent, which is still moist after rinsing with steam, is then ready for a further charging with crude aqueous liquid.

The ammonia employed for the extraction of. the adsorbent which contains in addition to the adsorbed accompanying substances also water from the moist adsorbent, is preferably subiected to a distillation under pressure for its separation from the water if its recovery in the liquid state for the purpose of employment again as an extraction agent cannot be dispensed with and it is not to be further worked up as gas.

In this case an evaporation at atmospheric pressure is sufiicient to separate the extracted substances in the form of a mixture of water and phenol almost free from ammonia.

The distillation under pressure is advantageously carried out in two parts. The greater part of the liquid ammonia may be conveniently driven over at slightly elevated temperature under a pressure of from 10 to atmospheres by employing waste heat at low temperature, such as that of eiiiuent warm cooling water orhot condensed water, without the use of a distillation column,

No appreciable amounts of extracted substances pass over and the distillate may be directly employed for fresh extractions. The remaining small part of the extraction solution. split up With residual small part of the extraction solution which remains after driving oi! the great part of the ammonia, it is advantageous, before u its further working up, to incorporate that part of the crude aqueous liquid which has absorbed gaseous ammonia during the emptying of the adsorption chamber from the aqueous liquids be- '0, fore the extraction with liquid ammonia, and also if desired the condensed aqueous liquid containing ammonia obtained when rinsing the extracted adsorbent with steam. In this manner it is possible, in spite of the great solubility of ammonia in .water, to restrlctthe waste of ammonia in continuous operation to a few per cent so that it is less than the waste of organic solvent in the known Ithasbeenfoundthattheprocessaccording to this invention offers considerable advantages as compared with the hitherto known. Given the same charging conditions for the adaorbent, there is needed according to this invention only about one sixth of the amount of extraction agent as compared with the usual employ- 'ment of benzene for this purpose. Apart from the great saving in time, there is also considerable saving in steam for heating for the working up of the extraction solution by distillation, not only by reason of the smaller amount oi solvent to be vaporized but also byreason of the possibility of using hot water as the heating means-for the distillation as already described.

In order to avoid high steam consumption in u the known benzene process" it has already been proposed .to free the benzene used from adsorbed phenols not by distillation but by extraction with caustic soda solution. Compared with the process according to this invention, this process has the a disadvantage that the extracted substances,

namely the phenols, are not separated as such but as phenolates.. I'br their further employment theymustfirstbeset freebymeansof carbon dioxide or strongmineral acids. This modified process thus requires two new raw materials, namely caustic soda solution and acid, and this toalargeextentcounteractsthesavinginsteam. A further advantage of the process according to this invention consists in the fact that the adsorptive power of the adsorbent subsides considerably more slowly by charging with crude aqueous solutions and subsequent extraction with liquid ammonia in continuously repeated operation than when employing the solvents hitherto proposed.

end of the charging periods are It has beenestablished for example that active carbon still retains more than 90 per cent of itsoriginal adsorptive capacity after far more than a hundred chargings in the removal of phenol from waste aqueous liquids from the destructive hydrogenation of coal, and subsequent extraction with liquid ammonia, while when using the same active carbon for the same purpose according to the benzene process under otherwise similar conditions, the adsorptive power is reduced-far below half within the same time.

The process according to the present invention has been found to be of particular advantage for the purification of aqueous liquids containing phenols which are obtained in hydrogenation processes, in particular the destructive hydrogenation, and further" in low temperature carbonization. But also aqueous liquids containing phenols which are obtained in cording to the present invention- As is known,

these aqueous liquids also contain certain amounts of tarry constituents.

The following examples relate to the removal of. phenol from hydrogenation waste aqueous liquids of three different concentrations in an adsorption chamber 5 meters in heightv containing liters of granular active carbon (8.8 kilograms) With each liquid there is carried out a wa'shing with ammonia and also. a washing with benzene for the purposeof comparison. For the repeated benzene would be even more unfavorable. Since when working up waste aqueous liquids, as for example waste water containing phenol,. they are usually only purified down to a certain final concentration, the average final concentrations of the eiliuent aqueous liquid from the beginning to the given.

It should be understood, however, that the present invention is not restricted to the following examples.

' Example 1 Phenol content in crude aqueous liquid gram per liter 0.750 Phenol content in final aqueous liquid gram per liter-.. 0.050 (Average value of the 22nd charging period) Throughput when using benzene liters per hour 40 Throughput when using liquid ammonia liters per hour 80 Benuns Liquid ammonia A t i u a fitgguogd qui mum mlitn's. P adsorbed lfisrams mom. Pigtails gech hgfialg: 2.5 per cent.... 4.1 per cent.

1 1 ma a--- kilograms. al ol v lzt a o ii logramsm- 13 kilograms. per cubic meter 0! crude aqueous liquid. 1

I other processes may v be worked up with advantage by the process ac- Example 2 Phenol content in crude aqueous liquid "grams per Men. 3.6 Phenol content in final aqueous liquid gram per liter 0.2 (Average value of the 40th charging period) Throughput when using benzene liters per hour 40 Throughput when using liquid ammonia "liters per hour 60 Benzene Liquid ammonia Amount of aqueous liquid 100 liters 280liters.

introduced in each charging P ex zfifidsorbed 340 grams 950 grams. Percentage of charging calcu- 5 per cent... 14 per cent.

laggd on the weight of car- Amount of solvent necessary" 35 kilograms.-. 16 kilograms. Amount of solvent necessary 350 kilograms.. 57 kilograms.

per cubic meter of crude aqueous liquid.

Example 3 Phenol content in crude aqueous liquid grams per liter 9.5 Phenol content final aqueous liquid gram per liter-.. 0.36 (The content of the final aqueous liquid in the case of benzene is the average concentration of the 45th charging period, in the case of liquid ammonia the average of 90th charging period.) Throughput when using benzene liters per hour-- 20 Throughput when using liquid ammonia .liters per hour 60 Benzene Liquid ammonia Amount of aqueous li uid in- 110 liters 270 liters.

trodiged in each 0 g P er iol adsorbed 1,000 grams 2,460 grams. Percentage oi charging, calcu- 14.7 percent. 36.2 percent and onthe weight of car- Amcfii nt oieolvent n.-. 70 kilograms-- 25 kilograms. Amount oi solvent necessary 640kllograms.. flakilograms.

per cubic meter oi crude aqueous liquid.

What we claim is:-

1. A process for the purification of aqueous liquids from phenols and other accompanying substances comprising tarry constituents which comprises treating such aqueous liquids with a solid adsorption agent, the said phenols and other accompanying substances thereby being adsorbed by the said adsorption agent and thereupon extracting the adsorbed phenols from the solid adsorption agent containing the same by treatment with liquid ammonia.

2. In the process as claimed in claim 1, starting from a liquid containing phenols which has been obtained by a process selected from the group consisting of hydrogenations and low temperature carbonization.

3. In the process as claimed in claim 1, continuously passing the aqueous liquid containing phenols and other accompanying substances through the adsorption agent and stopping the supply of the said aqueous liquid after the adsorption agent has taken up a substantial amount of phenols.

4. In the process as claimed in claim 1, treating the aqueous liquid with the solid adsorption agent, then removing from the solid adsorption agent the bulk of the liquid enclosing this adsorption agent by means of gaseous ammonia, and thereupon extracting the adsorbed phenols with liquid ammonia.

5. In the process as claimed in claim 1, extracting the phenols adsorbed by the solid adsorption agent by means of liquid ammonia and then removing trom the adsorption agent the bulk of "the liquid ammonia enclosing this adsorption agent by means of its own vapor.

6. In the process as claimed in claim 1, distilling from the liquid ammonia extract the bulk of the liquid ammonia under its own vapor pressure by warming to a slightly elevated temperature and llquefying again this distilled ammonia and subjecting the remaining portion of the liquid ammonia extract to a rectifying distillation, this portion thus being separated into ammonia and a mixture of water and phenols.

7. In the process as claimed in claim 1, treating the initial aqueous liquid with the solid adsorption agent, removing from the solid adsorption agent the bulk of the' liquid enclosing this adsorption agent by means of gaseous ammonia, separating from this bulk of the liquid the portion containing absorbed gaseous ammonia, extracting the solid adsorption agent containing adsorbed phenols with liquid ammonia, distilling from the liquid ammonia extract the bulk of ammonia, adding the betorementioned portion of aqueous liquid containing absorbed gaseous ammonia to the remainder of the liquid ammonia extract and then subjecting the resulting mixture to a rectifying distillation, the mixture thus being separated into ammonia and a mixture of water and phenols.

PAUL HERMANN GERICKE. PAUL HEROLD. HELMUT mATZ. EBERHARD VOGT. 

